The level and seasonal distribution of Vibrio parahaemolyticus will be determined in freshly harvested oysters (Crassostrea virginica), clams (Rangia cuneata, Mercenaria campechiensis) and mussels (Brachidontes recurvus, Modioulus demissus). Changes in the V. parahaemolyticus population because of handling in wholesale and retail channels also will be investigated. Similar studies will be carried out under controlled laboratory conditions to determine the effect of storage conditions (temperature and time) on population levels. Water and sediment samples from harvesting areas also will be examined. Isolations and enumeration of V. parahaemolyticus will be carried out both by direct plating and enrichment procedures. Oysters cultivated in ponds will be examined in the same manner. Data on the sampling conditions (time, depth, tide, etc.), water characteristics (temperature, salinity, pH, 02 content) and sanitary quality of shellfish samples (aerobic plate count, coliform and fecal coliform counts) will be used to examine possible relationships between level of V. parahaemolyticus and environmental conditions. To obtain information about the pathogenicity of V. parahaemolyticus, various strains, both Kanagawa positive and negative ones, will be tested against postlarval and adult crustacean shellfish, molluscan shellfish and against mice.